1. Field of the Invention
This invention relates generally to an apparatus and a method of application of the apparatus for detecting heart activity in which provision is made for sensing both the electrical energy and the sound energy of the heart.
In a more particular aspect, this invention relates to a small pick-up device that may be hand held and its method of application to a body in the region of the heart, for detecting electrical and mechanical activity of the heart and simultaneously generating signals useful in producing displays, such as electrocardiograms depicting the elemental P, QRS, T and U characteristic of electrical heart activity, and also displays, such as phonocardiograms of the heart sound energy.
2. Description of the Prior Art Stethoscope
The stethoscope is an instrument used for the detection and pneumatic amplification of sound within the body or chest, particularly heart sounds, that are coupled to the ears of the user through air columns defined within flexible tubes coupled to a pick-up bell or diaphram. The stethoscope is an instrument which is easy and convenient to use, but it has low diagnostic value because it requires the ear to do sub-second interpretation of complex sounds. Additionally, the frequency of response of the ear is not well suited to detecting the sounds of the body.
Electrocardiogram
The generation of electrocardiograms involves the use of multiple electrodes selectively disposed in different position groupings on the body for detecting electrical signals generated by heart motion. The display can be either a recording on graph paper or a cathode ray tube or both or other display device such as a liquid crystal matrix. The information obtained is a measurement of the electro conduction system of the heart. When properly used, the electrocardiogram will indicate a heart attack in progress or any destruction of heart tissue resulting from a heart attack. Evaluation of an electrocardiogram frequently requires comparison with prior electrocardiograms of the same patient to indicate changes in the heart function. In general, equipment for producing electrocardiograms is cumbersome and time consuming. The predictive value of the electrocardiogram is low. The use of such equipment is limited primarily to specialists such as cardiologists.
Phonocardiogram
Equipment for producing phonocardiograms utilizes a pick-up responsive to heart sound energy for producing electrical signals which are amplified and utilized to produce a display on graph paper or on a cathode ray tube, or both, or other display device of the heart sound energy. The response of the system including the transducer and the reproduction equipment for producing the display is extremely important so that none of the sound characteristics are lost in acquiring the signal. Existing phonocardiogram equipment is cumbersome and time consuming to use. It is relatively expensive and is not widely used except by cardiologists because of the difficulty of interpreting the complex signal displayed.
Echocardiogram
Equipment for producing echocardiograms differs from equipment discussed hereinabove in the sense that ultra sonic wave energy which is broadcast is reflected by organs of the body. These reflections are displayed and when the equipment is properly used and the displays properly interpreted, it is possible to evaluate the condition of the tissue and its motion if any. Here again, the equipment is cumbersome and the process of producing the echocardiogram is time consuming. Use of the equipment is limited almost exclusively to cardiologists.
Special Devices
Efforts to improve and miniaturize heart electrical energy and heart sound energy transducers are reflected in the following patents:
U.S. Pat. No. 3,858,005
Stethoscope With Display; inventor Robert A. Marshall; patented 31 Dec. 1974.
The patentee Marshall has modified the chestpiece of a conventional stethoscope to include a small cathode ray tube. The amplified outputs of crystal pick-ups disposed on the diaphram of the stethoscope chestpiece are displayed on the cathode ray tube, which is said to be a display of the heart sounds as in a phonocardiogaph.
U.S. Pat. No. 3,182,129
Electronic Stethoscope; inventor W. B. M. Clark et al; patented 4 May 1965.
The patentee Clark et al, commenting on the shortcomings of prior art devices with respect to limitations in their range of frequency response, their ineffective amplification of the lower frequency sounds as well as the higher frequency sounds, and their cumbersome physical characteristics, describes a stethoscope in which the transistor amplified output of a diaphram stressed crystal element is coupled to a speaker element such as an earpiece of a conventional hearing aid. Charts and graphs are provided to depict the improvement provided by this arrangement over that of the conventional acoustic stethoscope.
U.S. Pat. No. 3,960,141
Electro Surgical and ECG Monitoring System; inventor Lee R. Bolduc; patented 1 June 1976.
The patentee Bolduc simultaneously monitors a patient's beat-by-beat heart signal during an electro surgical procedure using an electrode structure in which the ground and pick-up electrode are combined in a single electrode structure. The pick-up electrodes are arranged on the ground electrode in a manner to minimize interference from the use of the electro surgical unit on the patient. Using suitable displays, the surgeon is provided with a display of the patient's heart action.
U.S. Pat. No. 3,455,293
Stethoscope Device; inventor R. W. M. Bethune; patented 15 July 1969.
The patentee Bethune utilizes the metal chestpiece rim of a conventional stethoscope as one electrode element of an electrocardiogram display device. In accomplishing this, one of the ECG leads is connected to a metal face of the stethoscope chestpiece. The heart sounds are conventionally acoustically coupled from the chestpiece to the earpiece of the stethoscope through flexible tubing.
U.S. Pat. No. 3,682,161
Heart Beat Transducer for a Monitoring Device; inventor Vernon F. Alibert; patented 8 Aug. 1972.
Using a principle similar to the patentee Clark et al above, the patentee Alibert mounts a plurality of piezoelectric crystal elements on a flexible element which is flexed by a diaphram element mounted in the transducer head and adapted to contact the body of a patient. The electrical output of the piezoelectric crystal elements is coupled to a suitable utilization device.